Fiber optic technology is increasingly employed in the transmission of data over communication networks. Networks employing fiber optic technology are known as optical communication networks, and are typically characterized by high bandwidth and reliable, high-speed data transmission.
To communicate over an optical communication network using fiber optic technology, fiber optic components such as fiber optic transceivers or transponders are used to transmit and receive optical signals. Generally, a fiber optic transceiver includes one or more optical sub-assemblies (“OSAs”) having an optical transducer. For example, transmitter optical sub-assemblies (“TOSAs”) have an optoelectronic transducer for transmitting optical signals, and receiver optical sub-assemblies (“ROSAs”) have an optoelectronic transducer for receiving optical signals. More particularly, a TOSA receives an electrical data signal and converts the electrical data signal into an optical data signal for transmission onto an optical network. A ROSA receives an optical data signal from the optical network and converts the received optical data signal to an electrical data signal for further use and/or processing. Both the ROSA and the TOSA include specific optical components for performing such functions.
In particular, a typical TOSA includes an optical transmitter such as a light emitting diode or a laser diode for transmitting an optical signal to an optical fiber. The optical transmitter is typically covered by an at least partially transparent cap that protects the optical transmitter while allowing the optical transmitter to transmit the optical signal to the optical cable. The cap may include a lens for focusing the optical signal transmission.
A typical ROSA includes an optical receiver, such as a PIN photodiode or avalanche photodiode (“APD”). The optical receiver is typically covered by an at least partially transparent cap that protects the optical receiver and allows the optical receiver to receive an optical signal from an optical cable. The cap may include a lens for focusing the optical signal transmission received from the optical cable.
One common problem in OSAs is backreflection. The term “backreflection” as used herein refers to a portion of an optical signal that is inadvertently reflected back towards the source of the optical signal. Backreflection can be problematic when the source of an optical signal is a sensitive optoelectronic transmitter. For example, the performance of some types of lasers, such Fabry-Perot lasers, can be affected by incident backreflection. The incident backreflection can act as undesirable optical noise that can interfere with optical signals produced by a laser. Backreflection can be problematic whether it occurs within a TOSA containing a sensitive optoelectronic transmitter, such as a Fabry-Perot laser, or whether it occurs in a distant ROSA, such as a ROSA connected to the TOSA by way of an optical cable.
Several attempts have been made at managing backreflection in OSAs. One such attempt involves the use of multiple components. However, such approaches generally add cost and complexity to the OSAs and/or are only marginally effective at managing backreflection within the OSAs. Therefore, a need exists for a solution to manage backreflection within OSAs.